p-chlorophenylalanine treatment accelerates tomato fruit ripening through hormone synthesis and glycolytic pathway during storage

Abstract

The accumulation of lycopene is the important indicator of tomato ripening and regulated by multiple plant signaling molecules. In this study, the effects of 30 μM p-chlorophenylalanine (p-CPA) on the postharvest ripening associated with lycopene content of tomato fruit were investigated during storage. The results showed that p-CPA treatment accelerated tomato fruit ripening, as indicated by increases in a* value, respiration rate and ethylene production, and decreases in firmness. p-CPA inhibited endogenous melatonin synthesis by competitive binding with tryptamine 5-hydroxylase (T5H), reducing the content of serotonin (the melatonin precursor), and down-regulating the genes expression of SlT5H, SlSNAT and SlASMT, while promoted ethylene synthesis and signal transduction by regulating the related genes. Meanwhile, p-CPA treatment enhanced the glycolytic pathway due to increasing the activity of 6-phosphofructokinase (PFK) and the contents of 3-phosphoglycerolaldehyde and pyruvate compared to the control. Also, p-CPA treatment enhanced the expressions of genes involved in lycopene synthesis including SlPSY1, SlPDS, SlZDS and SlCRTISO, thereby promoting the accumulation of lycopene. Thus, p-CPA treatment promoted tomato ripening along with lycopene accumulation by regulating endogenous melatonin and ethylene contents and activating glycolytic pathway during postharvest.